Injection access port with chamfered top hat septum design

ABSTRACT

An access port comprises a housing with a first opening and a self sealing septum sealing the first opening, the septum including an attachment portion for securing the septum to the housing, the attachment portion including a chamfer which, when the septum is mounted within the housing is subject to a force oriented substantially perpendicularly with respect to a plane of the outer surface, the chamfered portion redirecting a portion of the force to compress the outer surface. A septum for an access port comprises an attachment portion for abutting a septum seat of the access port and an operative surface permitting penetration by a needle and resealing itself after removal of the needle in combination with a chamfered portion providing a transition between the attachment portion and the operative surface, the chamfered portion re-directing a component of a force applied to the chamfered portion to compress the operative surface.

BACKGROUND OF THE INVENTION

Medical procedures for the treatment of chronic diseases often requirerepeated and prolonged access to a patient's vascular system to injecttherapeutic compounds and/or to sample or treat the patient's blood.Certain procedures are repeated often enough that it is impractical anddangerous to insert and remove the catheter and the needle from thepatient's vein at every session. Many patients are thus fitted with asemi permanent catheter to permit repeated access to the patient'svascular system.

Semi-permanently implanted catheters are generally designed to be assmall and thin as possible, to simplify the insertion procedure and toreduce discomfort to the patient. Access to such a catheter is typicallyprovided by one or more ports, which are in fluid connection with thecatheter and thus with the patient's vascular system. The port or portsgenerally have a very thin profile, so they may be implanted in thepatient with a minimum of discomfort. In most cases, such a port isimplanted subcutaneously, in a pocket formed surgically in the patient'schest or arm so that it lies just under the skin, in a location that iseasily accessible to medical personnel. More specifically, a septum ofthe port is positioned just under the skin so that therapeutic agentsmay be injected into the port through the skin and through the surfaceof the septum.

Insertion of therapeutic agents into the catheter is typically carriedout by injecting the fluid through the septum of the port, using theneedle of a syringe or a similar device. The septum includes at leastone surface that is capable of resisting damage cause by multiplepiercings from the needle, while re-sealing itself after the needle iswithdrawn. The service life of such ports is therefore limited by thedurability of the septum. After a certain number of punctures, theseptum becomes damaged and is no longer able to re-seal itself. Fluidsflowing in the catheter, such as blood, can then leak from the septumnecessitating replacement of the port and possibly of the entirecatheter. This procedure involves surgically opening the subcutaneouspocket, removing the damaged port from the catheter, and reinserting anew port with an undamaged septum. Replacing the port adds considerableexpense, inconvenience and discomfort to the procedure and increases therisk of infections and other complications.

SUMMARY OF THE INVENTION

In one aspect, the present invention is directed to an access portcomprising a housing with a first opening formed therein and a septummounted within the housing sealing the first opening, the septumincluding an outer surface covering the first opening and self-sealingafter penetration by a needle and an attachment portion for securing theseptum to the housing, the attachment portion including a chamfer which,when the septum is mounted within the housing is subject to a forceoriented substantially perpendicularly with respect to a plane of theouter surface, the chamfered portion redirecting a portion of the forceto compress the outer surface.

The present invention is further directed to a septum for an access portcomprises an attachment portion adapted to abut a septum seat of theaccess port and an operative surface adapted to permit penetration by aneedle and resealing itself after removal of the needle in combinationwith a chamfered portion providing a transition between the attachmentportion and the operative surface, the chamfered portion re-directing acomponent of a force applied to the chamfered portion to compress theoperative surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a perspective view of a injection accessport having a septum according to an embodiment of the presentinvention;

FIG. 2 is a diagram showing an exploded view of the injection accessport shown in FIG. 1;

FIG. 3 is a side elevation view of the septum according to an exemplaryembodiment of the invention;

FIG. 4 is a side elevation view of the septum according to anotherembodiment of the invention;

FIG. 5 is a side elevation view of the septum according to a thirdembodiment of the invention;

FIG. 6 is a side elevation view of the septum according to a fourthembodiment of the invention; and

FIG. 7 is a side elevation view of the septum according to a fifthembodiment of the invention.

DETAILED DESCRIPTION

The present invention may be further understood with reference to thefollowing description and the appended drawings, wherein like elementsare referred to with the same reference numerals. The invention isrelated to medical devices used to introduce fluids into a venouscatheter. Specifically, the devices according to the invention are usedto increase the useful life of venous ports that may be implanted in apatient to interface with an implanted venous catheter. However, thoseskilled in the art will understand that the present invention is equallyapplicable to a wide range of applications in which a port withpuncturing a self-sealing septum is implanted in the body. For example,although the invention is described for use with a port for theinjection of fluids, the port may just as well be used to withdrawfluids with no change in structure.

As described above, catheters are often semi-permanently implanted tofacilitate repeated access to a patient's vascular system. Suchcatheters may comprise a flexible elongated portion that extends throughtissue to enter a blood vessel or other organ. The proximal end of thecatheter may be connected to a port placed subcutaneously (e.g., in thechest or the arm) to provide access to the catheter.

The port allows fluids (e.g., chemotherapy agents, blood products,nutrients, therapeutic agents etc.) to be introduced into the patient'svascular system via a syringe or other similar device. The port is athin element generally connected directly to the catheter through anoutlet and having an inlet opening positioned so as to remainsubstantially flush with the patient's skin after implantation. When notin use, the inlet opening is sealed to prevent blood and other fluidsfrom leaking from the catheter, and at the same time to preventcontaminants from entering into the catheter. To that end, septa havebeen used to cover and seal the inlet openings of such ports. Such aseptum generally comprises a flexible membrane that overlies the inletopening and seals it with the material forming the septum being selectedfor its ability to continue sealing the port even after repeatedpunctures by a needle. For example, silicone or other elastomericmaterials have been used to form such septa.

In normal use, the septum is punctured with a needle whenever it isnecessary to inject a fluid into the port. Over time, the cumulativedamage degrades the material forming the septum so that, after beingpunctured a sufficient number of times, the septum is unable to re-sealitself after withdrawal of the needle. When the septum is still new, theelastic properties of the membrane tend to “bunch up” or push togetherthe edges of the hole left in the membrane by the puncture. As themembrane is used and the number of holes formed therein increases, theamount of elastic membrane material present around new punctures toclose the edges thereof decreases until new holes can no longer be fullyclosed. At this point, leakage through the operative membrane of theseptum begins.

The undesirable result described above is exacerbated if the membrane ofthe septum is placed under tension as the openings left by punctures arestretched when the membrane is under tension. In addition, tension maytear the membrane around the holes, so that over time the punctureopenings become larger and may tear through the membrane. The number ofpunctures that a septum may withstand depends on the size of the port,the material used, and the size of needles used to inject fluidstherethrough. As would be expected, larger needles cause more damagewhile a larger surface area septum provides more room to spread out thepunctures. High quality ports may withstand around 10,000 puncturesbefore replacement is necessitated.

Exemplary embodiments of a septum according to the present inventionimprove the durability of the corresponding venous port by reducingdegradation of the septum due to large numbers of punctures. As will bedescribed in greater detail, an increase in puncture damage resistanceis obtained by applying a compressive force to the septum membrane. Thecompressive force pushes together the edges of individual puncture holesand assists the elastic properties of the membrane in sealing suchholes. According to the present invention, the improvement to themembrane forming the operative surface of the septum allows an increasein the number of punctures that can be withstood by the septum beforeexcessive leakage requires replacement. Thus, the incidence of surgicalprocedures required to replace the port or the entire catheter isreduced.

FIGS. 1 and 2 show, respectively, a perspective view and an explodedview of a venous port having a septum according to an embodiment of thepresent invention. According to the exemplary embodiment, the port 100is designed to fit subcutaneously in a pocket surgically created in thepatient's chest, arm or other suitable location with a needle piercingmembrane facing outward. In this embodiment, the housing of the port 100is formed of two parts, a base 104 and a cover 102. For example, thebase 104 and the cover 102 may be secured together frictionally or witha mechanical interlocking connection, to prevent separation of the twocomponents after they have been placed within the patient's body. Aswould be understood by those skilled in the art, the exact shape of thebase 104 and the cover 102 may vary depending on the specificrequirements of the port design. Accordingly, the following descriptionis exemplary only and different configurations may be used to achievethe same results as described below.

The base 104 is designed to form a well 200 into injected into whichfluid injected into the port 100 is temporarily collected. The well 200is in fluid communication with an outlet opening 108 of the port 100,which in turn leads to a connection with a catheter (not shown). In oneexemplary embodiment, a valve 110 may be placed at the opening of theoutlet 108 to prevent undesired flow into or out of the catheter. Inthis exemplary embodiment, the cover 102 comprises a shroud portion 118designed to form an outer surface of the port 100, and a top portion 120defining an inlet opening 202. The top portion 120 is intended to beflush under the patient's skin when the device is implanted, so that aneedle can enter the opening 202 after piercing the patient's skin and aseptum 106 closing the opening 202. The shroud portion 118 may be shapedto interlock with the outlet portion 108 of the base 104, and may have acutout portion around the outlet opening 108 and the inlet opening 202is sized to substantially match the size of a septum 106, so that whenthe device is assembled, the inlet opening 202 is sealed by the septum106.

The septum 106 comprises a top membrane 112 that acts as the operativesurface of the port 100, through which the therapeutic compounds areinjected. The septum 106 may also include an attachment portion 114 tosecure the septum 106 in place within the port 100. In the exemplaryembodiment, the attachment portion 114 is an annular element thatsurrounds a periphery of the top membrane 112 extending outwardsubstantially perpendicularly therefrom. According to the presentinvention, a chamfer portion 208 provides a transition between theoperative surface of the membrane 112, and the attachment portion 114.The purpose of the chamfer portion 208 is to apply a compressive forceto membrane 112. In the exemplary embodiment, this force is provided bythe compression of the septum 106 between the base 104 and the cover 102when the port 100 is assembled. The shape and orientation of the chamferportion 208 re-directs the force applied by the assembled components ofthe port 100 to the septum 106, so that a component of that force actsradially inward along the membrane 112.

More specifically, the chamfer portion 208 of the septum 106 comprisesan annular surface 210 formed on an underside of the septum 106 facingthe base 104. The annular surface 210 is adapted to overlie and abut aseptum seat 204 of the base 104, when the port 100 is assembled. In thismanner the septum seat 204 provides an inner support to the chamferportion 208. When the port 100 is assembled by securing the cover 102 tothe base 104, the septum 106 is squeezed between those two components. Abottom bearing surface 206 of the cover 102 presses down on the chamferportion 208, squeezing it against the septum seat 204. The inner bearingsurface 201 of the cover 102 also applies a force radially inwardagainst the chamfer portion 208. The shape of the chamfer portion 208causes a component of the downward force applied thereto by the innerbearing surface to be re-directed radially inward along the surface ofthe membrane 112 around the periphery thereof, so that a compressiveforce is applied to the operative surface of the septum 106. Thus, thechamfer portion 208 gives to the septum a shape similar to that of a tophat.

As shown in FIG. 3, and more clearly illustrated in the enlarged view ofthe chamfer portion 208, a force F is applied to the chamfer portion 208when the base 104 and the cover 102 are assembled, with the septum 106sandwiched therebetween. Since the surface 116 of the chamfer portion208 is angled with respect to a direction of the force F, a forcecomponent F1 acting perpendicular to the surface 116 results. The forceF1 can be further divided into horizontal and vertical components toillustrate radially inward component F2 of the force F1. As the force Fis applied around the periphery of the surface of the membrane 112, theforce component F2 is directed radially inwardly around thecircumference of the membrane 112 compressing the membrane 112. Asdescribed above, this compressive force acting radially inward on themembrane 112 increases the tolerance of the membrane 112 to puncturedamage. In one exemplary embodiment, the chamfer portion 208 comprises aseparate angled surface 116 disposed at an angle of approximately 45degrees to the plane of the operative surface of the membrane 112 and,consequently, to the direction of the force F applied by assembly of theport 100. (Please provide a range for this angle) Those of skill in theart will understand that different angular orientations may be used tooptimize the septum 106 for various applications.

The combination of a properly shaped chamfer portion of a septum, and ofa venous port housing shaped to hold the septum in place thus providesan increased resistance to damage due to punctures through the septum.Although the present exemplary embodiment describes a port housingformed of two separate components, other housing configurations may besuccessfully used. According to the invention, when a force is appliedto the septum by the components of the assembled venous port, thechamfer portion of the septum may be designed to convert a component ofthat applied force into a compressive force acting radially inward alongthe operative surface. Different configurations of the port's housingmay thus be devised to apply the proper force to the septum when theport is assembled.

As will be understood by those of skill in the art, additional shapes ofthe septum's chamfer portion may be used. For example, FIG. 4 shows aseptum 400 according to a second embodiment of the invention, where thechamfer portion 408 comprises an angled surface 416 extending directlyfrom a top membrane 412 to an upper surface 418 of an attachment portion414. The angle at which the surface 416 is oriented may be selected toproduce desired characteristics of the septum. When the upper surface418 and the lower surface 420 are squeezed between a base and a cover ofthe corresponding venous port, the angled surface 416 causes a componentof the vertical force to be applied radially inward to compress theupper membrane 412. As described above, the result is an improvedability of the membrane 412 to re-seal puncture holes therethrough aftera needle is withdrawn.

A third exemplary embodiment according to the invention is shown in FIG.5. Here, the transition between an upper membrane 512 of the operativesurface and an attachment portion 514 is carried out by a step 516. Theprecise characteristics of the step 516 may be developed to obtain adesired compression in the membrane 512, and to facilitate the assemblyof the corresponding venous port. For example, the step 516 may besubstantially rectangular, with surfaces at right angles to the topmembrane 512, and to the sides of an attachment portion 514. In analternative embodiment, the surfaces of the step 516 may be oriented atdifferent angles, and may not be perpendicular and parallel,respectively, to the top and side surfaces of the septum 500.

FIG. 6 shows a side elevation view of a fourth embodiment of a tophat-shaped chamfered septum 600 according to the present invention. Inthis embodiment, the chamfer portion 608 comprises a curved fillet 616extending between the top membrane 612 of the operative surface and asurface of the attachment portion 614. In the exemplary embodiment, thecurvature of the fillet 616 has a substantially constant radius, howeveralternative designs may include variable radii to offer more complexcurves. The curved fillet 616 is preferably convex, to facilitatetransferring to the top surface 612 a compressive component of the forceapplied during assembly of the septum 600 in the corresponding port. Acurved fillet 616 may offer advantages in durability over chamferportions having more angular features, since fewer angles and edgeswhich concentrate stresses are present in the design.

Additional benefits with respect to the useful life of the septum may beobtained by using an oversized septum, in relation to the inlet openingof the venous port. For example, as illustrated in FIG. 7, a septum 700may include an operative surface comprising a top membrane 716, whichhas a larger diameter than the underlying inlet opening of the port. Asshown in the diagram, the inlet opening of the corresponding venous portmay have a diameter “d” which is smaller than the diameter of the topmembrane 716. Thus, when the operative surface of the septum 700 issqueezed into the inlet opening of the port, the side surfaces of theinlet opening of the port will apply a compressive force to the septum700. To maximize the useful life of the port, the oversized septum maybe fitted with any of the chamfer portions described above, so that acompressive force is applied to the top membrane 716.

According to the present invention, the assembly details of the venousport being assembled may dictate some of the design features of theseptum. For example, the angle taken by the surfaces of the chamferportion may vary to match the corresponding surfaces of the port. Thevarious dimensions and orientations of the septum's surfaces also mayvary, in accordance with the size and shape of the port in which theseptum is used. Accordingly, great latitude may be used within thegeneral shape of the top hat-shaped septum, according to the presentinvention, to fit the device in an appropriate venous port. As describedabove, many shapes of chamfer portions may be used to apply acompressive force to the operative surface of the septum, byre-directing a component of the force applied during port assembly. Thematerials used in forming the septum, as well as cost and ease ofassembly considerations may determine which specific design is selected.

The present invention has been described with reference to specificembodiments, and more specifically to a septum used in a venous catheterport. However, other embodiments may be devised that are applicable toother medical devices, without departing from the scope of theinvention. Accordingly, various modifications and changes may be made tothe embodiments, without departing from the broadest spirit and scope ofthe present invention as set forth in the claims that follow. Thespecification and drawings are accordingly to be regarded in anillustrative rather than restrictive illustrative rather thanrestrictive sense.

1. An access port comprising: a housing with a first and second openingsformed therein; and a septum mounted within the housing sealing thefirst opening, the septum including: a solid, disk-shaped operativeportion engaging the first opening and self-sealing after penetration bya needle; and an annular attachment portion for securing the septum tothe housing, the attachment portion being coupled to the operativesurface by a chamfered portion which, when the septum is mounted withinthe housing, is not coplanar with the annular surface and is subject toa force oriented substantially perpendicularly with respect to theannular surface, the chamfered portion redirecting a portion of theforce to compress the operative surface in a direction substantiallyparallel to the annular surface, wherein the chamfered portion comprisesan elastomeric material extending continuously, without interruption,along a cross-sectional plane, wherein the chamfer is not perpendicularto the operative surface and the annular surface, and wherein the secondopening is adapted to connect to a catheter and is substantiallyperpendicular to the first opening.
 2. The access port according toclaim 1, wherein a base of the housing forms a septum seat and a coverof the housing secures the septum on the seat so that the attachmentportion is compressed therebetween.
 3. The access port according toclaim 1, wherein the chamfer comprises at least one surface that formsan angle of between 0° and 90° relative to the operative surface and theannular surface.
 4. The access port according to claim 3, wherein the atleast one angled surface forms a 45 degree angle to the operativesurface.
 5. The access port according to claim 1, wherein the chamfercomprises a stepped surface extending away from the operative surface.6. The access port according to claim 1, wherein the chamfer comprises acurved fillet extending away from the operative surface.
 7. The accessport according to claim 6, wherein the curved fillet has a substantiallyconstant radius of curvature.
 8. The access port according to claim 1,wherein the annular surface abuts a septum seat of the housing.
 9. Theaccess port according to claim 1, wherein the operative surfacecomprises a substantially planar membrane overlying the first opening.10. The access port according to claim 1, wherein the operative surfacecomprises a membrane which, when unconstrained has a dimension greaterthan a corresponding dimension of the first opening so that, when placedwithin the first opening the operative surface is compressed thereby.11. A septum for an access port, comprising: an annular attachmentportion adapted to abut a septum seat of the access port, the attachmentportion including an annular surface; a solid, disk-shaped operativeportion adapted to permit penetration by a needle and resealing itselfafter removal of the needle, a periphery of the operative surface beingradially within a periphery of the annular surface; and a chamferedportion providing a transition between the annular attachment portionand the operative surface, wherein the chamfered portion comprises anelastomeric material extending continuously, without interruption, alonga cross-sectional plane, wherein the chamfered portion is not coplanarwith the annular surface and is not perpendicular to the operativesurface and the annular surface, and wherein the septum is a unitarybody.
 12. The septum according to claim 11, wherein the operativesurface is sized to substantially overlie an opening of the access port.13. The septum according to claim 11, wherein the chamfer portion isadapted to apply to the operative surface a radially compressivecomponent of a force applied substantially perpendicularly thereto byassembly of the access port.
 14. The septum according to claim 11,wherein the chamfered portion comprises a fillet joining the operativesurface to the attachment portion.
 15. The septum according to claim 11,wherein the chamfered portion comprises an angled surface that forms anangle of between 0° and 90° joining the operative surface to theattachment portion.
 16. The septum according to claim 11, wherein thechamfered portion comprises a stepped surface joining the operativesurface to the attachment portion.
 17. The septum according to claim 11,wherein the operative surface is formed of a flexible polymericmaterial.